<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        //in 检测某个对象中是否含有某个属性，不论公有和私有  有 true  没有 false
            function Fn(name,age){
			    this.name=name;
			    this.age=age;
			}
			
			var f1=new Fn("lili",18); 
            console.log(f1);
	
			console.log("age" in f1);//true
			console.log("toString" in f1);//true
            console.log("num" in f1);//false
    </script>
</body>
</html>